A stifled smirk and a cheerful wave as he was led from the dock to serve a minimum of 35 years behind bars were the only signs of emotion shown by Ali Koc throughout his five-week trial.

The 30-year-old declined his right to speak at Woolwich Crown Court, leaving victims’ families in the dark as to his motives for the series of vicious attacks which claimed the lives of two pensioners.

Police have been left scratching their heads and Judge Mr Justice David Calvert-Smith put it down to “violence for violence’s sake”.

But letters from Koc’s family, submitted to the bench on the day of sentencing, paint a desolate picture of a life without purpose.

Koc and his family moved from Turkey to their house in Lightfoot Road, Hornsey, in 1996 to join his father.

Koc made few friends and spent most of his days smoking cannabis while watching violent films and listening to music in his room, according to accounts from his sisters.

Koc had convictions for carrying a knife, robbery and possession of Class B drugs before the double murder and assaults.

He only left the house to have a flutter at a few local betting shops, sign on at the job centre, draw his state benefit from the Post Office and replenish his stocks of cannabis.

But in the days leading up to the brutal beatings the Department for Work and Pensions (DWP), for unknown reasons, blocked his benefit.

It is believed this triggered the unexplained behaviour which saw Koc stalk Alexandra Park, Priory Park, Downhills Park and Queen’s Wood for vulnerable victims, although one of Koc’s sister said she thought the drugs had taken their toll.

On January 31 last year Koc made repeated calls to staff at the DWP, becoming aggressive and resorting to racist abuse.

Enraged, he then dialled 999 to complain about the service.

At 1.26pm an operator called Koc’s home, but the killer had already left for Queen’s Wood where he would attack his last victim John **SHOULD THIS BE KEITH??** Needell and leave him for dead.

Officer on the case Det Chief Insp Tim Duffield said: “Koc has never shown any remorse for this wanton spate of attacks. There was no motive.”

Detectives are not ruling out the possibility that Koc may have attacked other people and have urged any potential victims to call police on 020 8358 0400 or Crimestoppers anonymously on 0800 555 111.